Novel Buxus papillosa-assisted green synthesis of copper and nickel oxide nanoparticles with enhanced catalytic degradation of alizarin red S dye

In this work, the biogenic synthesis route using the leaf extract of Buxus papillosa was employed for the green synthesis of copper oxide (CuO) and nickel oxide (NiO) nanoparticles (NPs), which were then applied for the catalytic degradation of Alizarin Red S dye (ARS) as a model organic pollutant. Scanning electron microscopy (SEM) analysis confirmed spherical and rod-like morphologies for CuO and NiO NPs, respectively, while Energy dispersive spectroscopy (EDS) verified their elemental composition. The average crystallite sizes of CuO and NiO NPs were 6.21 and 5.94 nm, respectively, as determined by X-ray diffraction (XRD), and their optical band gaps were estimated as 3.63 eV and 3.32 eV from UV–Vis analysis. The degradation kinetics followed a pseudo-first-order model with rate constants of 0.037 min −1 (CuO) and 0.031 min −1 (NiO), while Langmuir isotherm fitting (R 2 > 0.98) indicated monolayer adsorption. After 75 min, CuO and NiO NPs removed 73.32 ± 1.85 and 71.50 ± 2.07% of ARS dye, respectively, which increased to 96.01 ± 1.16 and 90.83 ± 1.43% with NaBH 4 addition. Both catalysts maintained >90% efficiency up to five reuse cycles, demonstrating high stability and reusability. These results confirm the potential of Buxus papillosa -derived CuO and NiO NPs as sustainable and effective nano-catalysts for wastewater treatment. • Green-synthesized CuO and NiO nanoparticles using Buxus papillosa extract. • XRD confirms monoclinic CuO (~6.2 nm) and cubic NiO (~5.9 nm). • SEM/EDS show spherical CuO and needle-like NiO with phytochemical capping evidenced by FTIR. • In NaBH 4 -assisted ARS degradation, CuO reaches 96% and NiO 91% dye removal with in 75 min. • Both NPs retains ≥90% dye degradation over three cycles and stays effective through five.